Purification of vinyl chloride

ABSTRACT

A method for removing unsaturates, particularly diolefins such as butadiene, from vinyl chloride, by contacting the impure vinyl chloride with catalytic amounts of a Lewis Acid such as aluminum chloride.

United States Paten 1191 McFadden Mar. 27, 1973 [54] PURIFICATION OF VINYL CHLORIDE [75] Inventor: Russell Thomson McFadden,

Freeport, Tex.

[73] Assignee: The Dow Chemical Company,

Midland, Mich.

22 Filed: Aug. 10,1970

21 Appl.No.: 62,724

[52] US. Cl. ..260/656 R [51] Int. Cl ..C07c 21/06 [58] Field ofSearch ..260/656 R, 656 AC, 652 P,

[56] References Cited UNITED STATES PATENTS 3,125,607 3/1964 Keating et al 260/656 R Primary Examiner--Leon Zitver Assistant Examiner-Joseph A. Boska Attorney-Griswold & Burdick and Raymond B. Ledlie 7] ABSTRACT A method for removing unsaturates, particularly diolefins such as butadiene, from vinyl chloride, by contacting the impure vinyl chloride with catalytic amounts of a Lewis Acid such as aluminum chloride.

3 Claims, No Drawings chloride,

PURIFICATION OF VINYL CHLORIDE The present invention relates to a novel and improved method for purifying impure vinyl chloride by removing certain unsaturated impurities therefrom and more particularly relates to a method for removing diolefins such as butadiene from vinyl chloride without a significant deleterious effect upon the vinyl chloride.

For some time the problem of contamination of vinyl chloride with other unsaturated compounds has been recognized and numerous processes have been proposed to effectively remove such impurities. By way of illustration, US. Pat. No. 3,125,607 shows a process whereby the impure vinyl chloride is chlorinated at low temperatures to convert the butadiene contained therein to the more easily separated chlorinated derivates. U.S. Pat. No. 3,125,608 provides butadiene removal by hydrogenating the impure vinyl chloride at high temperature and pressure in the presence of a supported Group VIII metal catalyst. U.S. Pat. No. 3,125,609 shows the catalytic removal of butadiene by contacting the impure vinyl chloride at elevated temperature with cupric chloride supported on an inert substrate such as alumina. Other methods such as selective solvent extraction to remove acetylenic and dienic compounds are likewise known.

It is an object of this invention to provide a novel and improved process for the purification of vinyl chloride. A further object is to provide a method whereby diolefins and other unsaturated impurities are removed from vinyl chloride at moderate conditions 'of temperature and pressure by employing an improved catalyst. These and other objects and advantages of the present process will become apparent from a reading of the following detailed description of the invention.

It has now been discovered that 1,3-butadiene and other undesirable impurities are removed from vinyl chloride at moderate conditions of temperature and pressure by contacting the impure vinyl chloride with a catalytic amount of a Lewis Acid.

The Lewis Acids suitable as catalysts herein include aluminum chloride, hydrocarbon complexes of aluminum chloride, aluminum bromide, aluminum iodide, ferric chloride, ferric bromide, ferric iodide, stannic chloride, stannic bromide, stannic iodide, zinc zinc bromide, zinc iodide, zirconium tetrachloride, titanium tetrachloride, boron trifluoride, and the like. In general, it is preferred to employ AlCl FeCl BF or their soluble complexes as the catalyst. Aluminum chloride and the hydrocarbon complexes of aluminum chloride have been found particularly suitable in many instances.

Such Lewis Acid catalysts are usually employed in concentrations of from about 0.5 to about 2.0 percent by weight based on the total weight of the mixture. The proportion of catalyst which is most effective varies somewhat based on the conditions employed and on the activity of the particular Lewis Acid employed. Concentrations of catalyst in excess of 2.0 wt. percent may be employed but, in general, no advantage is gained thereby.

It is generally preferred to employ a temperature during the catalytic reaction step of between about 40 and about 75C. At temperatures less than about 40C., the activity of the catalyst decreases markedly and at temperatures above about 75C., high autogenous pressures are generated and side reactions, particularly dehydrochlorination reactions, are promoted.

For effective removal of diolefins, it is important to provide a molar ratio of catalyst to diolefin of between about 1:5 to about 1:25, preferably from about 1:5 to about 1:20. Catalyst concentrations higher than about 1:5 result in excessive vinyl chloride losses and concen- -trations lower than about 1:25 lose effectiveness in diolefm removal.

Contact times between the vinyl chloride and the catalyst which are sufficient to reduce the level of impurities may vary over a wide range depending on a number of factors such as effectiveness of mixing, impurities present, catalyst employed,'reaction conditions and degree of impurity removal which is desired. In general, effective contact times are from about 1 minute to about 60 minutes with from 5 minutes to 15 minutes frequently being preferred.

The most commonly encountered impurity in vinyl chloride and usually the impurity present in the highest concentration is 1,3-butadiene. In addition to removing this impurity to low levels, however, the presentinvention likewise significantly reduces the concentration of other unsaturates such as chloroprene and vinyl acetylene.

The catalytic reaction employed to remove the diolef'm from vinyl chloride is preferably conducted at autogenous pressure but additional pressure may be employed to maintain the vinyl chloride in the liquid phase and therefore in contact with the catalyst.

One preferred method of conducting the process of the present invention is to add the impure vinyl chloride to a pressure vessel, admix the Lewis Acid catalyst therewith, agitate the mixture under autogenous pressure at a temperature of between about 40C. and about C. for a time sufficient to reduce the diolefin content to the desired level and remove the purified vinyl chloride from the vessel. Separation of the vinyl chloride. from the catalyst and from the heavies produced thereby is easily achieved by distillation. This process may be conducted either as a batc process or continuously.

EXAMPLE 1 A mixture of impure vinyl chloride and other chlorinated hydrocarbons was employed which had the following composition as determined by vapor phase chromatography:

vinyl chloride 72.5% by weight vinyl acetylene 400 ppm chloroprene 1,900 ppm LEI-butadiene 430 ppm 1,2-dichloroethylene (cis and trans) 0.53% by weight vlnylldenc chloride 10.8% trichloroethylene 0.37%

other saturated chlorocarbona balance Stannic Experiment Aluminum Ferric Designation Chloride Chloride Chloride A 1.0 gm.

B 0.2 gm

C 1.0 gm

D 0.25 gm E 0.50 gm F 0.99 gm G 2.00 gm The ampoules were then sealed, warmed slowly to 25C., and then tumbled at 70C. for 60 minutes. The liquids were found to have the following compositions:

A B o D E F G Vinyl chloride,

percent 71. 6 73. 2 70. 7 73.6 78. 72. 8 71. 2 Vinyl acet ene,

.p.n1. 480 380 10 340 280 290 77 Chloroprene,

, p.p.m 1,800 1,600 25 1,400 800 20 25 1,3-butadieme,

{1.13.111 50 50 50 50 50 50 50 1,2-dichloronthylenes percent .52 .51 .55 .51 .51 .51 51 Vinylidenc chloride, porcont 11.0 10. 5 11.0 10.3 10. 4 10.6 10.0 Triclllornethylene, pctcont .39 .38 .40 .38 .37 .37 .42 Other chlorocarbons Bal. Bal. Bal. Bal. Bal. Ba]. Ba].

EXAMPLE 2 In the same manner as Example 1, mixtures were prepared containing 1.0 percent aluminum chloride. These mixtures were tumbled at 70C. for l, 10, 20, and 60 minutes and the products had the following composition:

1 min. 10 min. 20 min. 60 min. Vinyl chloride,% 72.1 70.3 65.0 70.9 Vinyl acetylene,ppm 170.0 130.0 40.0 27.0 Chloroprene,ppm 25.0 25.0 25.0 25.0 1,3-Butadiene,ppm 10.0 24.0 10.0 10.0 1 ,Z-Dichloroethyl enesfk .52 .57 .64 .63 Vinylidene chloride 10.7 1 1.0 12.6 10.8 Trichlorocthylene .38 .42 .48 .39 Other chlorocarbons Bal. Bal. Bal. Bal.

EXAMPLE 3 In the procedure of Example 1, mixtures were prepared containing 0.50 weight percent of aluminum chloride and tumbled at 45C. for 5, 10, 20 and 40 minutes. The products had the following composition:

5 min. 10 min. 20 min. 40 min. Vinyl chloride,% 72.6 73.4 73.1 73.3 Vinyl acetylene,ppm 190.0 170.0 170.0 180.0 Chloroprene,ppm 25.0 25 .0 25.0 25 .0 1,3-Butadiene,ppm 10.0 10.0 10.0 10.0 1,2-Dichloro- .53 .52 .53 .55 ethylenes,% Vinylidene chloride,% 10.8 10.5 10.6 10.5 Trichloroethylenefk .39 .46 .36 .41 Other chlorocarbons- Bal. Ba]. Ba]. Ba].

EXAMPLE 4 In the same manner as Example 1, a liquid, soluble complex of aluminum chloride was added to 100 gm. quantities of impure vinyl chloride. The complex was prepared by mixing at about 7080C. a mixture of 1.0 mol of aluminum chloride, 2.0 mols of benzene, and 1 .0 mol of diethyl benzene. The vinyl chloride mixtures, in which the catalyst complex was freely soluble, were tumbled at 70C. for 1 hour. Results were as follows:

Concentration of Complex A l-gallon stainless-steel pressure vessel was built equipped for continuous metered input of impure vinyl chloride, having the composition shown in Example 1, and the aluminum chloride liquid complex catalyst, as prepared in Example. 4, for internal temperature control from 25 to 120C, for pressure operation up to 200 psig, and for continuous liquid phase removal. This reactor was operated'continuously so as to pump into the reactor 2.0 ml/minute of catalyst as a 50 volume percent solution in o-dichlorobenzene and 0.1 1 lb/minute of vinyl chloride. Throughout the operation the temperature of the liquid in the reactor was maintained at C. and the vapor pressure at about 100 psig. Liquid was withdrawn continuously so as to maintain a liquid volumev in the reactor of about /gallon. Samples were taken every 30 minutes during a two hour period, and analyzed as follows:

First Second Third Fourth Orig. sample sample sample sample liquid Vinyl CI,% 64.4 72.0 67.8 70.4 73.4 Vinyl acetyl- 200.0 190.0 165.0- 190.0 320.0

ene,ppm Chloro- 0.44 0.58 0.84 0.76 1.50 prene,% 1,3-Butadi- 28.0 53.0' 140.0 65.0 660.0 ene,ppm Catalyst 1.04 0.76 0.57 content,% Average con- 15 minutes tact time I claim:

1. A process for the purification of vinyl chloride which comprises contacting in the liquid phase, vinyl chloride containing diolefin impurities with a catalytic quantity of a Lewis Acid Catalyst selected from the group consisting of AlC1 FeCl BE, and soluble complexes thereof at a temperature of between about 40C. and about C., under autogenous pressure for a time sufficient to reduce the diolefin content thereof by con-- version of the diolefins to heavies, and thereafter separating the vinyl chloride from the heavies and catalyst.

2. The process of claim 1 wherein the concentration of the catalyst is from about 0.5 to about 2.0 weight percent of the total weight of the mixture.

3. The process of claim 1 wherein the molar ratio of catalyst to diolefm in the impure vinyl chloride is from about 1:5 to about 1:25. 

2. The process of claim 1 wherein the concentration of the catalyst is from about 0.5 to about 2.0 weight percent of the total weight of the mixture.
 3. The process of claim 1 wherein the molar ratio of catalyst to diolefin in the impure vinyl chloride is from about 1:5 to about 1:25. 